Visualization of El Nino southern oscillation events on distributions grassland and shrub-steppe birds

Objective

There are many wintering bird species that are irruptive or alter their wintering location from year to year. The reasons for this are unknown, but could be linked to large scale climatic events that alter available resources. Additionally, it is important to understand the full range of a species’ winter distribution, and migration corridors so that the full range of areas used under various climatic conditions can be targeted for conservation. This visualization examines the distribution and migration patterns of 14 bird species during El Nino, La Nina, or neutral years.

Codes:

ENSO El Nino southern oscillation

BASP Baird’s Sparrow, BRSP Brewer’s Sparrow, BTSP Black-throated Sparrow, CASP Cassin’s Sparrow, CCLO Chestnut-collared Longspur, GRSP Grasshopper Sparrow, LALO Lapland Longspur, LCSP LeConte’s Sparrow, MCLO McCown’s Longspur, SAGS Sagebrush Sparrow, SAVS Savannah Sparrow, SEWR Sedge Wren, SMLO Smith’s Longspur, VESP Vesper Sparrow

Winter Distributions

CCLO change or expand their winter range in El Nino years, SMLO change or expand their winter range in El Nino and La Nina years, and LCSP and SEWR expand their winter range in La Nina years. The other species visualized do not have any obvious winter range shifts.

Seasonal movements

BRSP

Brewer’s sparrows seem to move north earlier in El Nino years, and seem to have a more concentrated winter distribution in La Nina years compared to neutral years.

BTSP

Black-throated sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.

CASP

Cassin’s sparrows are unique in that they migrate east-west. This east west migration with some northward movement is visualized below. It appears like migratory patterns may be more widely distributed during La Nina years.

CCLO

The summer distribution of chestnut-collared longspurs seems more diffuse in La Nina years, while the winter distribution seems more concentrated in La Nina years, and more spread out in El Nino years. Additionally, in El Nino years chestnut-collared longspurs seem to migrate earlier and both arrive on their non-breeding range earlier, and leave their non-breeding range earlier.

GRSP

Grasshopper sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.

LCSP

LeConte’s sparrows expand their wintering range in La Nina years, and concentrate their wintering range in El Nino years. Additionally, they migrate north earlier in La Nina years.

MCLO

McCown’s longspurs have a relatively small breeding range and a wider wintering range. McCown’s longspurs may migrate south earlier in El Nino years.

SAGS

Sage sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.

SAVS

Savannah sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.

SEWR

Sedge wrens show fairly consistent migratory patterns regardless of climatic year type, however, they expand their winter distribution slightly in La Nina years.

SMLO

Smith’s longspurs may shift their range substantially based on climate, however, there were fewer observations for this species the apparent shifts could be due to data defiencies.

VESP

Vesper sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.

Data Description

This dataset is a subset of a publicly available data of species distributions from the USGS BISON site. The data is presence only data, and contains information compiled from a variety of sources ranging from museum specimens from the 1700s to current datasets based on field observations. The dataset includes information pertaining to the location and date of detection of species, along with information about the source of the data. I downloaded and combined information for several bird species and added information on ENSO (El Nino southern oscillation) events (La Nina, El Nino, and neutral) for years between 1897-2016 in the dataset. The final dataset after combining and manipulating data contains 2,015,999 observations and 19 variables, and includes combined information for 14 species of shrubsteppe or grassland associated bird species.

Data Source

US Geological Survey (USGS). 2017. Biodiversity Information Serving Our Nation (BISON). Available online at: https://bison.usgs.gov/#home; accessed 5/20/2017.

National Oceanic & Atmospheric Administration (NOAA). n.d. El Niño Southern Oscillation (ENSO). Available online at: https://www.esrl.noaa.gov/psd/enso/past_events.html; accessed 5/20/2017